Overview
ISO 719:2020, "Glass - Hydrolytic resistance of glass grains at 98 °C - Method of test and classification," specifies a laboratory method to measure hydrolytic resistance of glass grains and a classification system based on that measurement. The test quantifies alkali released from glass grains during extraction at 98 °C and expresses results as the volume of acid needed for titration or as the equivalent sodium‑oxide (Na2O) content. ISO 719:2020 is intended primarily for less resistant glasses (e.g., soda‑lime glass); more resistant glasses are covered by ISO 720.
Key Topics and Requirements
- Test principle: Extraction of 2 g of glass grains (particle size 300–500 µm) in CO2‑free test water at 98 °C for 60 minutes, followed by analysis of the extraction solution to determine alkali release.
- Measurement: Titration of released alkali with standard HCl (commonly 0.01 mol/L); results expressed as acid volume or Na2O equivalent.
- Sample preparation: Crushing, sieving (500 µm and 300 µm meshes), magnetic removal of iron particles, and cleaning. Minimum sample handling and pretreatment procedures are specified to avoid contamination.
- Reagents and water quality: Use of CO2‑free test water (methyl red neutral point pH 5.5 ± 0.1) and water conductivity ≤ 1 µS/cm. Use analytical‑grade reagents; fresh acetone is required for cleaning.
- Apparatus and controls: Class A burettes/pipettes/volumetric flasks, thermostatically controlled heating bath capable of maintaining ~98 °C, sieving equipment, ball mill, ultrasonic cleaner and ovens. Glassware pretreatment procedures are specified to prevent cross‑contamination.
- Result expression and classification: Clause 9 defines calculation, classification categories and designation rules (users must refer to the standard for the exact class thresholds).
Applications and Users
ISO 719:2020 is used by:
- Quality control and R&D laboratories in glass manufacturing (especially soda‑lime glass producers).
- Pharmaceutical and medical device manufacturers assessing glass containers, labware and components for chemical durability.
- Regulatory and procurement teams specifying material performance for packaging and laboratory equipment.
- Test laboratories performing compliance testing aligned with pharmacopoeial requirements.
Typical applications include verifying chemical durability of glass containers, comparing glass batches, and supporting material selection for products that contact aqueous media at elevated temperatures.
Related Standards
- ISO 720 - Hydrolytic resistance of glass grains at 121 °C (for more resistant glasses).
- ISO 385, ISO 565, ISO 648, ISO 1042 - referenced laboratory glassware and sieving standards.
- Harmonisation notes: ISO 719:2020 aligns key procedural elements with the European Pharmacopoeia and USP to simplify global laboratory application.
Keywords: ISO 719:2020, hydrolytic resistance, glass grains, 98 °C, testing method, classification, soda‑lime glass, alkali release titration, laboratory testing, pharmaceutical glassware.